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Re: ISSUE-3 and RDF simple entailment

From: Uli Sattler <sattler@cs.man.ac.uk>
Date: Fri, 29 Feb 2008 17:04:40 +0000
Message-Id: <51E1375C-47F7-4935-9610-1746E5ECCF1E@cs.man.ac.uk>
Cc: Jim Hendler <hendler@cs.rpi.edu>
To: "Web Ontology Language ((OWL)) Working Group WG" <public-owl-wg@w3.org>

On 29 Feb 2008, at 15:02, Jim Hendler wrote:

>
> The aspect of Jeremy's message that troubles me (but was probably  
> clear to many in the WG) is that we would have OWL DL 1.0  
> entailments that would not be OWL DL 1.1 entailments, this means we  
> would have breaks in interoperability between our 1.0 legacy and  
> our 1.1. proposal in DL - My group makes heavy use of Pellet, but  
> doesn't really need most of the new expressivity, so we would find  
> this troubling (esp. if we could not upgrade to a new version of  
> Pellet because it would break our demos).  In minor cases,  
> carefully annotated, this would be ok, but if we do major breaks  
> from previous versions this would be a problem.  We see this one as  
> falling somewhere in between - because it is hard to tell whether  
> it arises in some of the cases we use.  Guess this is that  
> backwards compatibility thing -- anyway, guess this is to say in  
> this case we could probably live with either solution, but if we do  
> break the old entailments, then we would really need careful  
> documentation of where this arises in real use (c.f. when we're  
> processing a lot of FOAF stuff with a bunch of bnodes through the  
> incremental version of Pellet, should we be worried?)

I don't think there is any reason for worries: the way Pellet has  
treated bnodes is the same as the one described in the proposed OWL  
DL 11 semantics. So you would get the same answers, and now it would  
even fit in with the spec.

Cheers, Uli

>  -JH
>
>
> On Feb 29, 2008, at 8:54 AM, Michael Schneider wrote:
>
>> Hi Jeremy! Hello David!
>>
>> Jeremy Carroll wrote on Friday, February 29, 2008:
>>
>>> One question that came up in HP discussion was whether the proposed
>>> resolution to ISSUE-3 would break the monotonicity requirement for
>>> semantic extensions
>>> http://www.w3.org/TR/rdf-mt/#MonSemExt
>>>
>>> I suggested that the proposal does break this requirement.
>>
>> AFAICT, this topic is only relevant for languages which claim to be
>> "semantic extentions" as defined by [10]. In this way, RDF  
>> semantics is a
>> semantic extention to Simple Entailment, RDFS to RDF, and both  
>> OWL-1.0-Full
>> and pD* are semantic extentions to RDFS. This is the "layered"  
>> approach
>> which I described in [20]. In fact, the "delta to OWL-1.0-Full  
>> idea", which
>> we discussed in an earlier telco, would mean that OWL-1.1-Full is  
>> becoming a
>> semantic extention to OWL-1.0-Full.
>>
>> But neither OWL-1.0-DL nor OWL-1.1-DL claim to be such a kind of  
>> semantic
>> extention to RDFS. So you cannot reasonably apply the "General  
>> monotonicity
>> lemma" from the RDF(S) semantics spec to them, where you have to  
>> "Suppose
>> that Y indicates a semantic extension of X".
>>
>>> Here are the
>>> test cases, are these correct?
>>>
>>> Here is a simple test case:
>>>
>>> A:
>>> _:a rdf:type owl:Thing.
>>> eg:dp rdf:type owl:DatatypeProperty .
>>> _:a eg:dp "foo".
>>>
>>> B:
>>> _:b rdf:type owl:Thing.
>>> eg:dp rdf:type owl:DatatypeProperty .
>>> _:b eg:dp "foo".
>>>
>>> A simple-entails B.
>>> A simple-entails A.
>>
>> Yes to both.
>>
>>> A owl-1.0-dl-entails B.
>>> A owl-1.0-dl-entails A.
>>
>> Not quite sure about this, but I believe to remember Peter saying  
>> so in some
>> telco. (I also remember that I was surprised about his answer at  
>> that time.)
>>
>>> A does not owl-1.1-dl-entail A.
>>> A does not owl-1.1-dl-entail B.
>>
>> If bNodes will be interpreted as skolems in 1.1-DL, then yes,  
>> these will be
>> non-entailments.
>>
>>> If I have understood some of the other aspects of OWL 1.1 DL then  
>>> also
>>> the following:
>>> C:
>>> _:c eg:dp "foo".
>>>
>>> D:
>>> _:d eg:dp "foo".
>>>
>>> C simple-entails C.
>>> C simple-entails D.
>>> C does not owl-1.1-dl-entail C.
>>> C does not owl-1.1-dl-entail D.
>>>
>>>
>>> Note: these show why this change while in keeping with Peter's
>>> characterization [1] of the relationship between OWL Full and OWL DL
>>> (OWL DL is weaker than OWL Full), misses the relationship
>>> between OWL DL
>>> and RDFS, which is - on the syntactic subset that is OWL DL, OWL  
>>> DL is
>>> stronger than RDFS.
>>
>> This may or may not be the case. Anyway, I would be very reluctant  
>> to make
>> this "observed" property a requirement for the DL flavours of OWL,  
>> now or in
>> the future. It has been the basic difference between OWL-1.0-DL and
>> OWL-1.0-Full that DL is semantically based on some specific  
>> description
>> logic (SHOIN(D) in the case of 1.0-DL), while Full is intended to  
>> be a
>> semantic extention to RDFS. These are two very different design  
>> principles,
>> so I wouldn't even easily come to the idea that OWL-x.y-DL might be
>> semantically a stronger language than RDFS.
>>
>> Under this pov, even the other direction, that OWL-Full is  
>> demanded to be
>> semantically a stronger language than OWL-DL, might become  
>> questionable. But
>> in this case, this property seems at least to be easier to obtain,  
>> since
>> these two languages share the same OWL specific language features,  
>> while
>> OWL-Full additionally consists of all the semantic properties  
>> inhereted from
>> RDFS. So this request looks quite reasonable to me.
>>
>> Bottom line: I *won't* demand OWL-1.1-DL to be a semantical upper  
>> language
>> to RDFS, but I *will* ask for OWL-1.1-Full being a semantical  
>> upper language
>> to OWL-1.1-DL.
>>
>> Cheers,
>> Michael
>>
>> [10] <http://www.w3.org/TR/2003/WD-rdf-mt-20030123/ 
>> #DefSemanticExtension>
>> [20] <http://lists.w3.org/Archives/Public/public-owl-wg/2008Feb/ 
>> 0068.html>
>>
>> --
>> Dipl.-Inform. Michael Schneider
>> FZI Forschungszentrum Informatik Karlsruhe
>> Abtl. Information Process Engineering (IPE)
>> Tel  : +49-721-9654-726
>> Fax  : +49-721-9654-727
>> Email: Michael.Schneider@fzi.de
>> Web  : http://www.fzi.de/ipe/eng/mitarbeiter.php?id=555
>>
>> FZI Forschungszentrum Informatik an der Universität Karlsruhe
>> Haid-und-Neu-Str. 10-14, D-76131 Karlsruhe
>> Tel.: +49-721-9654-0, Fax: +49-721-9654-959
>> Stiftung des bürgerlichen Rechts
>> Az: 14-0563.1 Regierungspräsidium Karlsruhe
>> Vorstand: Rüdiger Dillmann, Michael Flor, Jivka Ovtcharova, Rudi  
>> Studer
>> Vorsitzender des Kuratoriums: Ministerialdirigent Günther Leßnerkraus
>
> "If we knew what we were doing, it wouldn't be called research,  
> would it?." - Albert Einstein
>
> Prof James Hendler				http://www.cs.rpi.edu/~hendler
> Tetherless World Constellation Chair
> Computer Science Dept
> Rensselaer Polytechnic Institute, Troy NY 12180
>
>
>
>
>
Received on Friday, 29 February 2008 17:04:28 GMT

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